This invention relates to systems for measuring the composition of metal alloys and more particularly to an automatic, direct-reading instrument for non-destructively indicating the gold content of a metal object.
Medvinsky et al, in U.S. Pat. No. 4,799,999 issued Jan. 24, 1989, discuss problems of assay of precious metal objects and disclose a method with direct reading of alloy composition in which the test object is first anodized and then a potential generated by the anodized surface is observed as it decays. The potential decay information is compared with empircial data and, by interpolation, the approximate karat quality of the alloy is determined and indicated on a display.
The assay methods of the prior art that accurately indicate gold content over a broad range of composition require both time and skill. The direct reading devices that are fast and easy to operate fail to indicate precise gold content and distinguish between different precious metals.